1. Field of the Invention
This invention relates to primary backing for tufted carpets and carpets made therefrom.
2. Prior Art
A tufted carpet has at least two parts. The first is a primary backing and the second is tufted pile loops which usually pass through and are supported by said primary backing. In a tufted carpet, pile loops either cut or uncut project from one side and are usually connected by loops on the reverse or floor side.
Fine gauge tufting in the art implies tufting with about 10 or more tufting needles per inch in the weft direction. Fine gauges generally run from about 1/10 to about 1/20 inch, wherein in the weft direction 1/10 inch corresponds to 10 tufting needles per inch and 1/20 inch corresponds to 20 tufting needles per inch. Pile heights, deniers, and stitches per inch in the warp direction so vary from style to style, that no exhaustive correlation to fine gauge tufting can be made. Generally, in fine gauge tufting, pile heights are in the range from 3 mm to about 15 mm; pile deniers are in the range 75 tex to about 250 tex, but texes as high as about 300 are not unknown, and stitches per inch in the warp direction are in the range of about 8 to about 20. As the gauges become finer and pile heights shorter, any discontinuities arising from either needle or tape deflection become aesthetically very noticeable.
Woven-tape or woven slit film substrates such as disclosed in T. M. Rhodes (cited later) modified to include multifilament weft fibers give rise to an improved primary backing for use in fine gauge tufted carpets. However, many aesthetic problems arising from insufficient pile uniformity still occur. The stability of the tufted substrate is generally not sufficient to avoid bowing and skewing during dyeing or applying a foam backing. It is to be noted that distortion of the dyed image in fine gauge tufted carpets generally has a more critically adverse impact on the aesthetic appearance of said carpet than in other types of tufted carpets.
It is to be noted that attempts to stabilize the woven substrate by the application of adhesives so as to overcome the above cited problems often has an adverse impact on the tufted process and for that reason have been generally unsuccessful.
With the advant of synthetic primary backing such as disclosed by H. A. Schwartz et al. in U.S. Pat. No. 3,359,934 (1967) and by T. M. Rhodes in U.S. Pat. No. 3,110,905 (1963), the dyeability of the primary backing in general, and those made from polyolefins, such as polypropylene and polyethylene resins and the like in particular, has become a concern. The reason for this concern is that if the substrate is not dye-compatible with the pile fibers, i.e. does not accept the same dye-stuffs as the pile fibers, then the substrate will shadow light and detract from the overall light reflectance desired. Also the carpet will lack the desired uniform coloration and pattern clarity after pattern deep dyeing. For purposes of discussion, both of these undesirable aspects of a substrate which is not dye-compatible with the pile loops will be referred to as "grinning" problems.
Of the many methods tried to solve grinning problems, only needlebonding of a fiber dye-compatible with the pile loops in sufficient quantities to form a thin subsurface of fibers which visually covers said substrate has had widespread commercial success. The method of needlebonding a substrate is disclosed by R. H. Kimmel, et al. in U.S. Pat. No. 3,605,666 (1971). A primary backing made by this process of needlebonding will throughout this Specification be referred to as an FLW primary backing. FLW are initials for fiber lock weave. It is to be noted that the reason for using different types of fibers for the substrate from those used in the pile loops is dictated by commercial considerations, in that the dyeable pile loops generally are much more expensive than the material used to form the substrate of the primary backing.
There are however several disadvantages to both the manufacture and performance of FLW primary backing. These are: (1) production speeds for the needling process are very adversely affected by decreasing fiber deniers, increasing web weights, and increasing number of needle punctures/inch and also there is a substantial amount of noise associated with the needling process; (2) some of the effective covering power of the needled fibers is lost due to a portion of the needled fibers projecting through to the back of the substrate; (3) there is a tendency for some of the fleece fibers to work their way out of the FLW primary backing (fiber bleeding) with adverse affects on the performance and appearance of the finished carpet; (4) even though a greater cover power/web weight of pigmented, dyed or dye-compatible fibers occurs with increasingly fine deniered or low cross-sectional area fibers, in practice the cross-sectional area of the fibers in the needling process are limited, because the finer the fiber the slower is the process of needlebonding; (5) tuft lock (as measured according to ASTM D 1335-67) is reduced in a primary backing material which has been needled prior to tufting; and (6) the overall tensile strength of a tufted primary backing is reduced by the needlebonding process.
It is an object of this invention in some of its embodiments to provide a primary backing for fine gauge tufted carpets which overcomes many of the above described problems associated with fine gauge tufting.
It is an object of this invention to provide a method and article of manufacture suitable for primary backing for tufted carpets and carpets made therefrom which obviate the limitations associated with FLW primary carpet backings and their method of manufacture.
It is an object of this invention to provide an article suitable as a primary backing for tufted carpets which uses substantially less dyeable, pigmented, or dyed subsurface or fleece fibers than an FLW primary backing to achieve an equal degree of visual cover or cover factor.
It is an object of this invention to provide a primary backing for tufted carpets wherein the subsurface fibers have both a higher peel strength and substantially less tendency to fiber bleed than those found in FLW primary backing.
It is an object of this invention to provide a primary backing for tufted carpets which has higher overall tensile strength subsequent to a tufting and/or dyeing operation than an FLW backing.
Other objects will be clear to a man of skill in the art after reading this Specification.